Estimation of aortic BP waveform from noninvasive radial tonometry; validation of FFT and ARX methods

The objective of this research was to develop a method of estimating central aortic pressure (AA) waveform from the noninvasive radial tonometry (TRA) waveform. In order to attain this goal, the Fast Fourier Transform (FFT) and Auto-Regressive eXogenous (ARX) models were used to develop the transfer function (TF) between the AA (input) and TRA (output). The inverse TF was then derived to generate the AA waveform from the TRA waveform. To test the accuracy of the model, the aortic pressure waveform using a Millar catheter tip transducer and noninvasive radial artery waveform using a Colin tonometer were simultaneously obtained in 5 patients who were undergoing cardiac catheterization at Yamagata University. The inverse TF based on the FFT model did not accurately reconstruct the AA waveform. On the contrary, ARX model resulted in accurate estimate of AA with the estimation error of approximately 3% for systolic, diastolic and mean pressure levels. The noninvasive radial tonometry in combination with the ARX model may offer a potential of noninvasive estimation of aortic pressure waveform.